All the top users on Digg aggressively dugg each others submissions, that is undeniable. What's more, because of the "I'll vote your shit up if you vote mine up" mentality, and the ability to easily follow users to see what they submit and vote on, they also acquired hoards of normal users who would do the same without reciprocity in hopes of joining the top ranks.

It would've been a fairly worthless currency if not for the blogspam networks like Gizmodo, Engadget, Tech Crunch, Mashable, Cracked, Life Hacker, etc. that sprung up to funnel Digg's firehose of users on to ad-laden pages.

While no system would be perfect, Digg's made it excessively easy to game (maliciously or otherwise) and the content of submissions soon became almost irrelevant compared to who was submitting it.